1. Field of the Invention
The present invention relates to a laser beam machining head. More specifically, the invention relates to a laser beam machining head for feeding a filler wire, or having an electrode for various types of arc welding, such as inert gas shielded tungsten (TIG) arc welding, metal active gas (MAG) arc welding, and plasma arc welding, the head being useful as a tip machining optical system for laser beam machining.
The present invention is also useful when applied to a laser beam machining head of a laser beam machine for cutting or piercing a workpiece of a metal or the like.
2. Description of the Related Art
FIG. 21 is an explanation drawing conceptually showing a composite welding head according to an earlier technology. As shown in the drawing, a composite welding head 223 performs laser welding and TIG welding, and has two welding heads, i.e., a laser welding head 224 and a TIG welding head 225. With such a composite welding head 223, the same site of welding is machined with laser light and a TIG arc, so that it is impossible to set both welding heads 224 and 225 vertically relative to a base material 216. Thus, either the welding head 224 or the welding head 225 is inclined forward or rearward, namely, is given an angle of advance or an angle of backing to carry out welding. In FIG. 21, a tungsten electrode 210 at the tip of the TIG welding head 225 is inclined forward so that an arc 213 will reach a condensing site 206a for a laser beam 206.
FIG. 22 is an explanation drawing conceptually showing a filler wire-coaxial laser welding head 226 according to an earlier technology. As shown in the drawing, the filler wire-coaxial laser welding head 226 has a structure in which a filler wire 207 is passed through holes perforated at the center of a total reflection mirror 214 and an imaging lens system 204. The filler wire 207 and an optical axis of a laser beam are rendered coaxial, and the filler wire-coaxial laser welding head 226 is designed to perform welding while feeding the filler wire 207 via a filler wire feed pipe 208. With the filler wire-coaxial laser welding head 226, a laser beam 206 launched from an optical fiber 201 is reflected by the total reflection mirror 214, and condensed by the imaging lens system 204 for use in fusing a base material 216 and the filler wire 207. The filler wire 207 is fed by a filler wire feeder 209.
FIG. 23 is an explanation drawing conceptually showing a TIG arc-coaxial laser welding head 227 according to an earlier technology. As shown in the drawing, this TIG arc-coaxial laser welding head 227 arranges an electrode 210 for TIG welding and a laser beam optical axis coaxially, thereby performing TIG welding and laser welding simultaneously. Its constitution is basically the same as the constitution of the filler wire-coaxial laser welding head 226 shown in FIG. 22, the difference existing only in the electrode 210, an electrode holding pipe 211 for holding the electrode 210, and a welding power source 212.
FIG. 24 is a vertical sectional view showing the constitution of a tip portion of a conventional, typical laser beam machining head. A laser beam machining head 301 shown in the drawing is provided in a laser beam machine (its machine body is not shown) which cuts an object 302 to be cut, such as carbon steel.
As shown in FIG. 24, a lens-barrel 305 houses a condensing optical system (an imaging lens system) 304 composed of a plurality of lenses 310, and a protective glass 307 for protecting the condensing optical system 304. The condensing optical system 304 condenses laser light 303, and projects it onto a cutting site 302a of the object 302 to be cut. On this occasion, a focal position, f, of the laser light 303 condensed by the condensing optical system 304 is usually adjusted to lie within the object 302 to be cut, as illustrated in the drawing. The laser light 303 is generated by a laser oscillator such as a YAG laser oscillator (not shown), and then transmitted to the condensing optical system 304 by an optical transmission means such as an optical fiber or mirrors (not shown).
On a laser light ejection side of the condensing optical system 304 (i.e., a lower end portion of the lens-barrel 305), an assist gas nozzle 306 is attached in such a manner as to surround the laser light 303 that has been ejected from the condensing optical system 304. The assist gas nozzle 306 is shaped like a truncated cone with a tip side (lower end side) becoming thin, and has an opening 306a at the tip side. To a side surface of the assist gas nozzle 306, an assist gas supply pipe 308 is connected. The assist gas supply pipe 308 is tied to an assist gas supply device (not shown). That is, an assist gas Q.sub.T transported from the assist gas supply device is introduced into the assist gas nozzle 306 via the assist gas supply pipe 308, and is jetted through the tip opening 306a of the assist gas nozzle 306 toward the cutting site 302a of the object 302 to be cut.
A cutting operation for the object 302 to be cut, by means of the laser beam machine equipped with the laser beam machining head 301 of the above-described constitution, is performed in the following manner: First, the laser beam machining head 301 is brought close to the object 302 to be cut, by the use of a laser beam machining head moving device (not shown). Also, the distance between the tip of the assist gas nozzle 306 and the surface of the object 302 to be cut (i.e., work distance), h, is kept so that there will be no contact between the assist gas nozzle 306 and the object 302 to be cut. In this condition, either the laser beam machining head 301 is moved by the laser beam machining head moving device in a direction perpendicular to the sheet face of FIG. 24, or the object 302 to be cut is moved by a work moving device (not shown) in a direction opposite to the moving direction of the laser beam machining head.
In accordance with this movement, the laser beam machining head 301 condenses the laser light 303 by the condensing optical system 304, and projects it onto the cutting site 302a of the object 302 to be cut, thereby fusing the cutting site 302a. Simultaneously, an assist gas is jetted toward the cutting site 302a from the tip opening 306a of the assist gas nozzle 306, and introduced into the cutting site 302a, to blow away and remove fused metal within the cutting site 302a. Thus, the object 302 to be cut is laser cut.